A comparator is an analog device that compares the amplitude of two analog input voltage or current signals and generates a digital signal indicating whether one of the two analog input signals has a greater amplitude than the other. Although any high gain, differential amplifier may operate as a voltage comparator, precision advantages result from using a plurality of capacitively coupled, series connected, comparator stages. By storing charges that compensate for 1/f noise and a previous stage's output offset voltage on capacitors that couple the stages together, a highly precise comparison results.
However, when overdrive conditions occur, such multistage comparators suffer from an undesirably long recovery time. The recovery time represents the length of time needed to recover from a previous comparison before a subsequent comparison may occur. Successive approximation analog-to-digital (A/D) converters typically include a comparator for making a plurality of successive comparisons. The lengthy recovery time is especially undesirable when a multistage comparator is used in a successive approximation A/D converter application because an overall word conversion must be slowed to account for worst case recovery time on each bit in the conversion. Consequently, a need exists for a comparison circuit that has improved recovery time characteristics.